1. Field of the Invention
Embodiments of the present invention relate, in general, to expansion of tissue and particularly to biological tissue growth through tensile stress induced by unidirectional radial expansion of an implantable/removable device.
2. Relevant Background
It is well known that tissue growth can be initiated and sustained in response to a sustained tensile stress. Stress is defined as a force distributed over a finite area. The imposition of such a tensile force (stress) has taken many forms and has resulted in human tissue growth in many kinds of living tissue including skin, bone, muscle, nerves, blood vessels, lungs, and the like. The devices that create such a tensile force to promote tissue growth include hooks, springs, and other mechanical devices that attach to the various portions of the tissue so as to apply a sustained tension. These techniques are typically associated with reconstructive surgery, in which a portion of the human anatomy has been damaged and often require sustained non-ambulatory care. For this reason, procedures of this type for cosmetic surgery have not gained much acceptance and thus surgical implants are typically used. The use of implants does not create an environment supportive of tissue growth. As is described below, an implant is placed in a dissected region to fill an artificially created void. The implant thus becomes pseudo new tissue, eliminating the natural impetuous for tissue growth.
Non-invasive versions of devices offering ambulatory care to promote tissue growth are known in the art but have yielded inconsistent and minimal results. The non-invasive devices known in the art provide an irregular and inconsistent application of a slight suction to the skin in an attempt to produce a tensile force on the applicable tissue. In doing so the non-invasive procedure seeks uncontrolled and undirected tissue growth in the general region subjected to the suction.
While successful in promoting some tissue growth, non-invasive techniques share the common barrier of requiring daily user interaction resulting in inconsistent and often asymmetrical results. Additionally, it is well known that for tissue growth to occur, a tensile force should be applied on a consistent basis for extended periods of time. Misapplication of the device or inconsistent use, especially in the early stages of treatment, deters tissue generation. Devices of this type are typically cumbersome and awkward and restrict the user's day-to-day activity.
With respect to invasive techniques, the challenge has been to create a targeted environment for tissue growth that is both effective and yet allows the patient to continue with their day-to-day activities. In the past, inflatable devices have been utilized to dissect tissue layers to create an anatomic working space to facilitate the performance of laparoscopic or other minimally invasive surgical procedures including implantation. A surgical balloon dissector is inserted in a region and inflated to create a void in which an implant is placed. In contrast to traditional blunt dissection techniques, the dissection balloon creates the tissue pocket while respecting natural tissue planes or boundaries in the anatomy.
A second type of inflatable device or balloon, known as a tissue expander, has been utilized as a temporary implant to gradually expand a previously dissected pocket over time as the overlying skin and tissue gradually alters and expands in response to the fluid filled tissue expander. Such tissue expanders are typically left in place over a prolonged period of time to allow the cutaneous tissues to gradually alter and expand. Accordingly, periodic adjustment of the expander to add additional fluid is required as the tissue gradually expands over time. While growth in the skin and surrounding tissue is promoted, tissue growth in the void rarely occurs because the pocket or void is filled with the relatively solid tissue expander.
Breast augmentation has traditionally occurred using the aforementioned techniques followed by inserting one of two types of implants—silicone or saline. Saline implants are filled at the time of surgery with saline solution. Implants of this type can be inserted through very small incisions in a deflated form and after they are in place in the body, can be inflated to their final size. Silicone implants, which are implanted in their inflated state, are firmer and more noticeable beneath thin soft tissue and therefore, in most instances require placement underneath the pectoralis major muscle (sub pectoral placement). This adds to the length and complexity of the surgical procedure and time for surgical recovery. Both procedures require a foreign object, the implant, to remain within the body as no actual breast tissue is grown.